Early coverplates were used as windage covers disposed upon rotating gas turbine engine disks. More modern coverplates are also used to attain a cooling of the disk. An axial extension of the cover may extend into a broach area of a turbine disk (or rotor) radially outside the disk rim and radially supported by the blade. The coverplate is spaced radially from the disk to provide a dead ended annular space. Cooler air migrates to this space and insulates the disk rim from the engine's extremely hot working medium that is acting on the turbine blades. Tests have shown that this feature reduces the disk rim temperature by over 100 degree F. which increases the disk low cycle fatigue life and allows the use of less expensive material from which the disk is fabricated.